I believe you’ll need factory disc brake spindles (disc and drum spindles have different part #s) or new spindles with an aftermarket kit. Some good reading here to start with many additional posts you can search:

https://www.camaros.net/threads/69-disc-brake-conversion-nicer-kit-with-manual-brakes-vs-power-assist-and-oem-type-setup.486526/#post-1783341033

 

Yes they can. The factory drum and disc spindle are 99% the same. The 1% is the boss area at the top which is machined down to allow the backing plate and caliper bracket to mount up. I recommend getting the complete kit from “The Right Stuff” you can add power disc and be better equipped. I will discourage you (because I’ve done it) from just putting on disc brakes without replacing the master cylinder and proper brake valves. See the website for what you want and do your research.

Disc Brake Conversion Kits | Hydroboost Conversion Kits

Our Disc Brake Conversion lineup is the most complete on the market. Leading the way for Disc Brake Conversion Kits for many different makes, models, & years.

rpui.com

 

Brakes (pozziracing.com)

 

Thanks to everyone for consideration and your responses.
I’ve owned this car for about a year and it is very original… meaning a lot of things are 50+ years old…
I am sorting through quite a few things and it’s far from where I want it - it’s now drivable save for the brakes. It has a strong pull when braking so that must be sorted.

At some point down the road it will be getting a pretty thorough suspension update / upgrade. Front or four wheel disc brakes will be installed at that same time. Just haven’t decided on which kit combo will be right for me. I much prefer to wait and research than buy twice.
So I have decided in the near term to save a little money and refurbish the manual stock drums - metallic shoes, turned drums, new hoses, new wheel cylinders at all four corners. That will get me back on the road.

Separate question - Part of my plan for the suspension is a 2 inch drop. I like the idea of a drop spindle to retain full suspension travel but there seems to be a fair amount of hate for drop spindles in internet land…
Pros and cons?

My car will never be tracked - but I come from sports cars so I “enjoy” curvy roads…

 

So I have decided in the near term to save a little money and refurbish the manual stock drums - metallic shoes, turned drums, new hoses, new wheel cylinders at all four corners. That will get me back on the road.

Separate question - Part of my plan for the suspension is a 2 inch drop. I like the idea of a drop spindle to retain full suspension travel but there seems to be a fair amount of hate for drop spindles in internet land…
Pros and cons?

My car will never be tracked - but I come from sports cars so I “enjoy” curvy roads…

Better brake shoes, Metalic/Ceramic, will provide greater stopping along with a complete brake job (springs, cylinders, hoses, fluid flush). I have always done my own brake jobs on any car I have. However getting the hard pull to one side would occur on aggressive stops, especially if brakes were hot, even after several adjustments. For that reason I switched to a front disc kit. I have 14" rims so used the Right Stuff 14" kit which uses a 10 3/4" rotor and a single piston caliper. HUGE improvement on braking. The kit was $600 a few years ago.

My thread on the swap
Right Stuff Drum to Disk kit? | Team Camaro Tech (camaros.net)

On lowering the car, I used Ridetech Progressive lowering springs up front using stock control arms. 1 5/8" drop. They do include a template showing where to cut about 1/2 of the spring coil to go lower if you want but I did not do that. I did replace all A arm bushings & ball joints (Moog) when I did the springs. For rear I used 2" lowering blocks with 2-degree shims. I am happy with the stance and ride.

I did replace stock sway bar with a Summit brand 1 1/8" bar which also made a cornering improvement.

 

Not an answer to your new question but something to consider on the brakes. I have the Wilwood four wheel disc brake kit and the emergency brake is challenging to get to hold the car without adjusting so much that you have drag. I’ve seen similar experiences from other owners. You might consider front disc only and retain the factory drum/e-brake setup.

 

My $.02, unless you actively auto cross, front disc/rear drum is fine vs 4 wheel disc....and the associated costs associated with rear disc brakes

Regarding lowering the car, I would and did, lowering coil springs vs drop spindles. Look into the RideTech "progressive" lowering spring.

OP, also consider converting to power brakes when you do the swap. Use the 11" stock size booster and disc/drum (larger bore) MC. Several kits available but I installed the Right Stuff front disc kit

 

OP, I recently called 3 of the bigger manufacturers of suspension parts for first gen Camaros. I'd like to add all of them were great to speak to over the phone.
Two of them plus a shock company all said to stay away from drop spindles. The other that uses drop spindles, sells another kit to correct what the drop spindles do to the car. Doesn't sound like the best way to me. After some measuring, this additional system would have run into my headers.
I also was lucky enough to see all three of these companies' systems on different first gen Camaros within 10 minutes of me. After seeing some differences, it was easy for me to make my decision.
I'm going with upper and lower tubular control arms and coil over shocks for the front so I can drop the ride height to where I like it. It sounds like there are many ways to skin this cat, but I want my car to handle so that also influenced my choice.
A cheaper way to do drop the front end would be to cut the front springs or buy lowering springs. No suspension expert here, do your research.

 

An update….

“I have decided in the near term to save a little money and refurbish the manual stock drums - metallic shoes, turned drums, new hoses, new wheel cylinders at all four corners”….

Finally finished this job. I went with Porterfield brake shoes…
Braking performance is much better! But better than really shitty doesn’t mean it’s great. I will still go to front DB at some point. But for now it’s safe and didn’t cost a ton - so might be worth considering for a street cruiser…